The invention relates to color changers, and in particular to an improved color changer for selectively supplying different colors of paint to spray coating apparatus.
The prior art contemplates numerous color changers for controlling delivery of paint of selected colors to spraying apparatus, for preventing nonselected colors from being delivered to the apparatus and, usually, for flushing the system between color changes to clean it of one color of paint in preparation for supplying another.
Known changers have certain disadvantages, which often are the result of the characteristics of the paint to be used. For example, some paints include solids that should be maintained in uniform suspension throughout the supply system. If the paint flow is stopped for any significant time, solids tend to settle out of the desired suspension, producing a nonuniform coating when the paint is applied. Unless a color changer is able to maintain an adequate paint flow, it cannot satisfactorily handle such paints.
Other color changers use diaphragm-type valves to control the flow of paints. Such valves are prone to wear and early failure.
One known color changer is taught by U.S. Pat. No. 4,627,465. In the process of providing selected paint colors for spraying, the color changer also continuously recirculates both selected (i.e., those delivered to the paint applicator) and nonselected colors. The color changer is of a modular type, and a module is provided for each color to be selected. To accommodate recirculation of both selected and nonselected colors, each module has three separate and distinct valves and valve actuators, as a result of which a color changer constructed from the modules is mechanically complex and subject to increased risk o failure. For spray coating applications that do not require continuous recirculation of paint to and from the spraying device itself, the color changer is overly complicated.